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The inflammatory cytokine TNF-? promotes the premature senescence of rat nucleus pulposus cells via the PI3K/Akt signaling pathway.

ABSTRACT: Premature senescence of nucleus pulposus (NP) cells and inflammation are two common features of degenerated discs. This study investigated the effects of the inflammatory cytokine TNF-? on the premature senescence of NP cells and the molecular mechanism behind this process. Rat NP cells were cultured with or without different concentrations of TNF-? for 1 and 3 days. The inhibitor LY294002 was used to determine the role of the PI3K/Akt pathway. NP cells that were incubated with TNF-? for 3 days followed by 3 days of recovery in the control medium were used to analyze cellular senescence. Results showed that TNF-? promoted premature senescence of NP cells, as indicated by decreased cell proliferation, decreased telomerase activity, increased SA-?-gal staining, the fraction of cells arrested in the G1 phase of the cell cycle, the attenuated ability to synthesize matrix proteins and the up-regulated expression of the senescence marker p16 and p53. Moreover, a high TNF-? concentration produced greater effects than a low TNF-? concentration on day 3 of the experiment. Further analysis indicated that the inhibition of the PI3K/Akt pathway attenuated the TNF-?-induced premature senescence of NP cells. Additionally, TNF-?-induced NP cell senescence did not recover after TNF-? was withdrawn. In conclusion, TNF-? promotes the premature senescence of NP cells, and activation of the PI3K/Akt pathway is involved in this process.

SUBMITTER: Li P

PROVIDER: S-EPMC5314336 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

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The inflammatory cytokine TNF-α promotes the premature senescence of rat nucleus pulposus cells via the PI3K/Akt signaling pathway.

Li Pei P Gan Yibo Y Xu Yuan Y Song Lei L Wang Liyuan L Ouyang Bin B Zhang Chengmin C Zhou Qiang Q

Scientific reports 20170217

Premature senescence of nucleus pulposus (NP) cells and inflammation are two common features of degenerated discs. This study investigated the effects of the inflammatory cytokine TNF-α on the premature senescence of NP cells and the molecular mechanism behind this process. Rat NP cells were cultured with or without different concentrations of TNF-α for 1 and 3 days. The inhibitor LY294002 was used to determine the role of the PI3K/Akt pathway. NP cells that were incubated with TNF-α for 3 days ...[more]

PMID: 28211497

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Project description:BackgroundAccelerated cellular senescence within the nucleus pulposus (NP) region is a common feature of disc degeneration. Our previous work indicated that TNF-α promoted NP cell senescence. Although the intervertebral disc has been reported to be an estrogen-sensitive tissue, it is unclear whether estrogen can inhibit premature senescence of NP cells.ObjectiveTo investigate whether 17beta-estradiol (E2) can attenuate TNF-α-induced premature senescence of NP cells and the potential mechanism behind this regulatory process.MethodsIsolated NP cells and intact intervertebral discs from healthy rats were cultured with or without TNF-α, E2 or their combination. The pan estrogen receptor (ER) antagonist ICI 182780 was used to investigate the role of ER. Direct and indirect indicators including cell proliferation, SA-β-Gal activity, telomerase activity, cell cycle, and the expression of matrix macromolecules (aggrecan and collagen II) and senescence markers (p16 and p53) were used to evaluate the premature senescence of NP cells. Additionally, intracellular reactive oxygen species (ROS) and NF-κB/p65 activity were also detected in the NP cell cultures.ResultsIn the NP cell cultures, E2 significantly increased cell proliferation potency, telomerase activity and the expression of matrix macromolecules but attenuated SA-β-Gal activity, senescence marker (p53 and p16) expression and G1 cycle arrest in TNF-α-treated NP cells. Furthermore, E2 inhibited ROS generation and phospho-NF-κB/p65 expression in the TNF-α-treated NP cells. However, the ER antagonist ICI 182780 abolished the effects of E2 on TNF-α-treated NP cells. In the disc organ cultures, E2 also significantly increased matrix synthesis, whereas it decreased senescence marker (p53 and p16) expression, which could be abolished by the ER antagonist ICI 182780.ConclusionThe interaction between E2 and ER can attenuate TNF-α-induced premature senescence of rat NP cells through interfering with the ROS/NF-κB pathway.

Project description:Luteolin (3',4',5,7-tetrahydroxy flavone) is a flavonoid, which is widely distributed in various plants including flowers, vegetables, and medicinal herbs and spices. Luteolin can be applied in the treatment of various diseases due to its multiple biological activities, such as anti-inflammatory, anticancer, and antioxidative activity. However, its role in intervertebral disc degeneration has not been previously reported. Therefore, the purpose of the present study was to explore the effects of luteolin on Tumor necrosis factor (TNF)-α-induced inflammatory injury and senescence of human nucleus pulposus cells (HNPCs), as well as the underlying mechanisms of action of this compound. Cell viability and apoptosis were assessed by MTT assay and TUNEL staining, respectively. ELISA kits were applied to detect the levels of inflammatory cytokines and the activity of telomerase. Senescence β-galactosidase staining was used to detect the activity levels of β-galactosidase in the cells. Cell transfection was performed to achieve interference of sirtuin 6 (Sirt6). The protein expression levels were detected by western blot analysis. TUNEL staining and western blot analysis were performed to assess the expression levels of apoptosis-related proteins. The results indicated that TNF-α induced a significant decrease in HNPC viability and an increase in inflammatory factor levels, while the application of luteolin effectively increased cell viability and decreased intracellular interleukin (IL)-1β and IL-6 expression levels. Furthermore, luteolin decreased apoptosis compared with the TNF-α groups in a dose-dependent manner. In addition, the results of the detection kits suggested that luteolin reversed TNF-α-induced senescence. Notably, interference with Sirt6 partially reduced the protective effect of luteolin on TNF-α-induced HNPC senescence via the Sirt6/NF-κB pathway. In summary, the data indicated that luteolin suppresses TNF-α-induced inflammatory injury and senescence of HNPCs via the Sirt6/NF-κB pathway.

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The inflammatory cytokine TNF-? promotes the premature senescence of rat nucleus pulposus cells via the PI3K/Akt signaling pathway.

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The inflammatory cytokine TNF-α promotes the premature senescence of rat nucleus pulposus cells via the PI3K/Akt signaling pathway.

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